•The rock-cutting characteristics of the disc cutter under abrasive water jet precutting kerf conditions are studied.•The effects of kerf depth and cutting spacing on rock-breaking performance are ...investigated, and efficient combined rock-breaking parameters are obtained.•The expansion of the main crack during rock cutting by the disc cutter under abrasive water jet precutting kerf conditions is dominated by tensile damage.•Deeper kerf depth reduces the rock-breaking load of disc cutter, but it does not benefit the sprouting and expansion of cracks inside the rock.
To reveal the rock-breaking mechanism of the disc cutter under the front-mounted water jet precutting kerf conditions and study the effect of water jet kerf depth (H) and cutter spacing (S) on rock-breaking performance. The rock-cutting test and numerical simulations by disc cutter under the water jet precutting kerf conditions are conducted. The effects of H and S on the rock-crushing state, rock-cutting force, and rock-breaking efficiency are investigated, and the failure mechanism of internal rock cracks is revealed and discussed. The results show that with the increase of H, the disc cutter's vertical force and rolling force can be reduced by 48.2% and 32.9%, respectively, at maximum, but fail to improve the internal crack expansion capacity of the rock. The optimal combination of S of 80 mm and H of 9 mm can promote the expansion of the main crack and improve the rock-cutting efficiency. Meanwhile, the numerical simulations result further show that the microcrack initiation and propagation can describe the rock damage process. The rock internal crack initiation stage is accompanied by tensile and shear cracks, while the crack propagation stage is dominated by tensile cracks. Microscopic observation of the scanning electron microscope (SEM) reveals that the fracture mechanism for the major crack is tensile type.
Display omitted
•DEM is used to model the cathode structure evolutions during calendering.•A comparison between simulation with corresponding tomographic scans was made.•Electrochemical analysis was ...performed using the idealised DEM structures.•The workflow enables rational insight into the battery electrode calendering.
Electrode microstructure can profoundly affect the performance of lithium-ion batteries. In this work, the effect of the calendering process on electrode microstructures is investigated using the Discrete Element Method (DEM) with a bonded particle model. A comprehensive evaluation between realistic electrode structures and idealised DEM structures as characterised using X-ray computed tomography (XCT) is presented. The electrode structural and transport properties of tomography scans and DEM structures, i.e. porosity distribution, specific surface area and tortuosity factors are studied. Following consideration of the carbon binder domain (CBD) phase, electrochemical analysis is further performed. Excellent agreement between tomography and idealised structures from DEM simulations is achieved, taking into account the effect of calendering. With electrode compression battery performance is improved after calendering. This study provides a basis for using DEM and electrochemical analysis to quantitatively evaluate the battery performance in future.
Display omitted
•We deal with two-dimensional meso-scale numerical approaches on concrete fracture.•Concrete is modelled as a random heterogeneous 4-phase material.•The concrete micro-structure is ...based on X-ray micro-computed tomography images.•The fracture simulations are carried out with FEM and DEM.
The paper describes two-dimensional meso-scale numerical results of fracture in notched concrete beams under quasi-static three-point bending. Concrete was modelled as a random heterogeneous 4-phase material composed of aggregate, cement matrix, interfacial transitional zones (ITZs) and air voids. Two different approaches were used: a continuum and discrete one. The concrete micro-structure in calculations was directly taken from real concrete specimens based on 3D X-ray micro-computed tomography images and 2D images by the scanning electron microscope. Attention was paid to the shape of a fracture zone between aggregate grains. In addition, the property effect of ITZs on fracture was studied.
•The progressive face failure of a shield tunnel in sand is analyzed.•The coupled FDM-DEM is adopted.•The effect of particle shape on the failure process is investigated.•Results of soil movement, ...surface movement and supporting force are presented.•The force chains and distribution of microscopic contacts of particles are analyzed.
The face failure of tunnels has been extensively studied. However, the effect of particle shape on the failure process still remains unclear. In this paper, the progressive face failure of a shield tunnel in sand is analyzed with coupled discrete element method (DEM) and the finite difference method (FDM) in three-dimension. Soils at the tunnel face, where large deformation occurs and continuum mechanics description does not apply, are modeled with DEM. And the FDM is used for the rest areas where deformation and displacement are relatively small. In order to obtain appropriate parameters for soils as reference, a series of triaxial tests on both loose and dense soils are conducted. The face failure is generated by moving the tunnel forward and backward, which, respectively, simulates the collapse failure corresponding to the tunneling speed higher than soil excavating speed and the blow-out failure corresponding to the converse case. In particular, the effect of particle shape on the failure process is investigated in detail by adopting tetrahedral particles, elongated particles and spherical particles with rolling resistance coefficient of 0.0, 0.1, 0.2 and 0.4. The soil movement, ground surface movement, supporting force of the tunnel face, and the distribution of microscopic contacts are analyzed during the progressive failure of the tunnel face, which demonstrate a significant effect of particle shape.
•A CFD-DEM model simulated heat transfer between plastic and sand in a rotary furnace.•Loading solid heat carriers in the kiln can promote the heat transfer for pyrolysis.•The volatile residence time ...in the kiln increased with the loading of heat carriers.•Increasing the solid heat carrier loading could reduce the wax yield from pyrolysis.•Loading more heat carriers favored the production of pyrolysis oil and gas.
The increasing plastic wastes have become a serious concern to the environment. Plastic wastes could be efficiently converted to fuel via pyrolysis. In the process of plastic pyrolysis, the key process parameters will affect the production of the final product, the distribution of pyrolysis gas, pyrolysis oil, and pyrolytic wax. Based on previous experiments, the discrete element model and computational fluid model were established in this study to compare the influence of heat carrier loading and furnace rolling speed on the pyrolysis of waste plastics in a rotary furnace. The simulation results indicate that when the granular heat carriers were loaded, as the heat carrier loading increased, the translational velocity and angular velocity of the waste plastic particles increased. Compared with the heat carrier-free case, the heating rate of the waste plastic particles is greatly increased when the heat carrier was loaded. The increase in the heat carrier loading also increased the residence time of the pyrolysis volatiles in the rotary furnace. With the acceleration of the rolling speed of the furnace, the translational velocity and angular velocity of plastic particles all increased, but the improvement of heat transfer efficiency is not obvious. This is consistent with the insignificant change in the pyrolysis product in the previous experimental results. The CFD-DEM simulation (excluded the pyrolysis reaction model) provided detailed information on particle movement, heat transfer and volatile residence time which could be used as an effective tool to interpret the experimental observation and optimize the process parameters.
This study first reviewed theories of the mechanical response of structures under loading, and the discrete element method provides a route for studying mechanical response including elastic ...deformation and structure failure. However, the direct acquisition of the microscopic parameters from the governing equations of the discrete element method via experiments encounters challenges. One possible strategy to obtain these microscopic parameters is parameter calibration that are widely used by researchers. Secondly, the governing equations and failure criterion of the discrete element method are summarized, and the microscopic parameters that would be calibrated are pinpointed. Next, the principles of classical calibration methods of discrete element method are explicated in detail, alongside the validation and discussion of their properties. Lastly, this study examined the applicability of calibrated parameters and points out that the size ratio, porosity, maximum radius, and minimum radius of particles should be identical in both the geometric calibration model and that for applications.
The preparation of colloidal gels containing different amounts of platelet and sphere-like powders is presented for the production of textured structures using robocasting and templated grain growth ...methods. The influence of platelet amount on paste fabrication and extrusion is investigated experimentally and numerically. Rheology of the pastes showed the need to vary coagulant and total filling fraction to obtain a paste suitable for robocasting. Pastes containing up to 0.15 platelet fractions were successfully extruded through 0.5 mm and 1.5 mm nozzle diameters. Pastes with platelet content higher than 0.18 and different filling fractions could only be extruded through the 1.5 mm nozzle. Discrete Element Method simulation predicts that the extrusion of pastes containing a high amount of platelets through a thinner nozzle was not possible due to powder morphology and size. Thus, the simulation supports the assumption that a high amount of platelets might be unprintable using thinner nozzles.
•The cellular automata concept is embedded into the GWO.•CGWO with a topological structure can help to improve diversity of population.•The proposed CGWO can solve multimodal problems well.•The CGWO ...outperforms the other state-of-the-art algorithms on function and engineering problems.
Grey wolf optimizer (GWO) is a newly developed metaheuristic inspired by hunting mechanism of grey wolves. The paramount challenge in GWO is that it is prone to stagnation in local optima. This paper proposes a cellular grey wolf optimizer with a topological structure (CGWO). The proposed CGWO has two characteristics. Firstly, each wolf has its own topological neighbors, and interactions among wolves are restricted to their neighbors, which favors exploitation of CGWO. Secondly, information diffusion mechanism by overlap among neighbors can allow to maintain the population diversity for longer, usually contributing to exploration. Empirical studies are conducted to compare the proposed algorithm with different metaheuristics such as success-history based adaptive differential evolution with linear population size reduction (LSHADE), teaching-learning based optimization algorithm (TLBO), effective butterfly optimizer with covariance matrix adapted retreat phase (EBOwithCMAR), novel dynamic harmony search (NDHS), bat-inspired algorithm (BA), comprehensive learning particle swarm optimizer (CLPSO), evolutionary algorithm based on decomposition (EAD), ring topology PSO (RPSO), crowding-based differential evolution (CDE), neighborhood based crowding differential evolution (NCDE), locally informed particle swarm (LIPS), some improved variants of GWO and GWO. Experimental results show that the proposed method performs better than the other algorithms on most benchmarks and engineering problems.
More and more earthquake cases demonstrate that sandy deposits may be more prone to becoming liquefied again in aftershock events. This phenomenon has also been authenticated by some laboratory ...element tests and shaking table tests. However, most of the existing studies on reliquefaction only put particular emphasis on the completely reconsolidated soil. Due to the possible short time interval between the main shock and its aftershock events, the generated pore pressure in soil deposits may not have completely dissipated when the aftershock occurred; the reliquefaction is more likely to occur under incomplete consolidation conditions. To investigate the reliquefaction behaviors and the related microscopic mechanisms for the incompletely and completely reconsolidated soil, a series of numerical cyclic triaxial tests are performed in this study via the 3D Discrete Element Method (DEM). Results demonstrated that the reliquefaction resistance of soil is significantly affected by the residual strain and the reconsolidation degree. From the microscopic point of view, the fabric anisotropy and the tightness of inter-particle contacts are the main factors affecting the reliquefaction resistance.
In this paper, the influence of particle shape on the permeability of porous media is investigated through the lattice Boltzmann method (LBM). The accuracy of LBM is verified by comparing the ...theoretical solutions and the numerical results of face-centered cubic (FCC) arrays of spheres. The porous media consisting of ellipsoidal particles with different aspect ratios was generated by the Discrete Element Method (DEM), and the aspect ratio a/c and the shape parameter ψ (ratio of sphericity to roundness) is introduced to quantify the particle shape. After that, the fluid flow in porous media of arbitrary particle shapes is numerically studied by LBM, based on which, the effects of porosity, tortuosity, and particle shape on the permeability characteristics of porous media are analyzed. It is found that the porosity function n3/(1-n)2 and tortuosity function showed a highly linear correlation with permeability, and the shape parameter ψ is more suitable for expressing the shape correction coefficient CF. On this basis, the equation based on the classic Kozeny-Carman (K–C) equation is developed to predict the permeability of porous media involving the particle shape effect. To verify the accuracy of the equations, the constant head test is conducted for porous media samples with regular arrangements of ellipsoidal particles produced by the 3D printing technique. The experimental results show that the prediction results of the prediction equation in this paper are closer to the experimental results and have higher accuracy compared with the other empirical equations.
•The influence of particle shape on the permeability of porous media is numerically studied by using the lattice Boltzmann method (LBM).•The Discrete Element Method (DEM) is used to generate the particles of different shapes, and the aspect ratio and ratio of sphericity are used to quantify the particle shape.•The equation to predict the permeability of porous media involving particle shape effect is proposed.•The 3D printing technique is used in the experiments and the efficiency of the proposed equation is evaluated.
PDF
